Ceramic filters are well known in the electrical art and at least one ceramic filter is described in U.S. Pat. No. 4,431,977 for a "Ceramic Bandpass Filter".
Prior art ceramic bandpass filters are constructed from blocks of ceramic material, are relatively large and are typically coupled to other electronic circuitry through discrete wires, cables, and pins coupled to connection points on external surfaces of the blocks.
It is also well known that some major objectives in electronic designs are reduced physical size, increased reliability, improved manufacturability, and reduced manufacturing costs. To achieve these somewhat conflicting objectives, electronic circuits are increasingly being manufactured using so-called surface-mount techniques.
Surface-mount is a manufacturing technique by which electronic components are attached to a circuitry substrate without using metallic leads that extend from a package or electronic component. A surface mountable ceramic block filter is described in co-pending application Ser. No. 07/661,025 for a "Monolithic Surface Mount Ceramic Bandpass Filter" filed Feb. 25, 1991, which application, as is this application, is assigned to Motorola, Inc.
In manufacturing a ceramic block filter, prior art ceramic block filter manufacturing techniques have typically used abrasive methods to remove metallization or have used various screen printing techniques to apply conductive material onto the various surfaces of the ceramic block in order to electrically tune the filter. These prior art techniques depend upon very close tolerance abrading or very fine patterning, both of which are difficult to achieve in a manufacturing environment.
In addition to patterning metallization on a block to tune or adjust its electrical characteristics, input-output contacts or pads, which are typically isolated areas of conductive material, must also be formed on at least one side of the block. Careful abrasion and/or patterning to produce very small dimensioned input/output pads as well as top patterns and very fine line screen printing is difficult and costly to achieve.
In a surface mount ceramic block filter, in which the input/output pads for a block filter are required to be closely mated to the supporting substrate, an improved structure for providing connections or input/output terminals to a block filter would be an improvement over the prior art.